mysql 5.5与5.6 timestamp 字段 DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP的区别.
5.6: [BIGHD](root@127.0.0.1) [cm]> SELECT version(); +------------+ | version() | +------------+ | 5.6.13-log | +------------+ 1 ROW IN SET (0.02 sec) [BIGHD](root@127.0.0.1) [cm]> ALTER TABLE s__uk ADD `last_op_time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP; Query OK, 0 ROWS affected (0.99 sec) Records: 0 Duplicates: 0 Warnings: 0 [BIGHD](root@127.0.0.1) [cm]> SELECT id, last_op_time FROM s__uk LIMIT 1; +----+---------------------+ | id | last_op_time | +----+---------------------+ | 1 | 2013-10-10 10:17:57 | +----+---------------------+ 1 ROW IN SET (0.00 sec) 5.5: (root@localhost) [cm]> SELECT version(); +------------+ | version() | +------------+ | 5.5.15-log | +------------+ 1 ROW IN SET (0.00 sec) (root@localhost) [cm]> ALTER TABLE s__uk ADD `last_op_time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP; Query OK, 2523 ROWS affected (0.99 sec) Records: 2523 Duplicates: 0 Warnings: 0 (root@localhost) [cm]> SELECT last_op_time FROM s__uk LIMIT 1; +---------------------+ | last_op_time | +---------------------+ | 0000-00-00 0 | +---------------------+ 1 ROW IN SET (0.00 sec)
另外，有没有考虑过如果只更新这个字段会怎样？会是指定的时间，还是自动生成的时间？
(root@localhost) [cm]> UPDATE s__uk SET last_op_time='2012-12-12 0' WHERE id=1; Query OK, 1 ROW affected (0.07 sec) ROWS matched: 1 Changed: 1 Warnings: 0 (root@localhost) [cm]> SELECT id, last_op_time FROM s__uk LIMIT 1; +----+---------------------+ | id | last_op_time | +----+---------------------+ | 1 | 2012-12-12 0 | +----+---------------------+ 1 ROW IN SET (0.01 sec)
猜对了木有？
PS: 如何判断字段中是否有多字节字符（比如中文）?
CHARACTER_LENGTH(value) = length(value) 则不包含多字节字符。
length为字节Bytes长度， CHARACTER_LENGTH为字符characters长度。
PS2: mongodb find()之后美化/格式化输出的函数是： db.tbl.find().pretty()
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